1. Field of the Invention
The present invention relates to a stamped knitting tool for textile machines, particularly knitting machines, of the type which generally includes a shank provided with at least one butt and with the shank having at least one closed or open-edged free space, hole or opening filled with a heterogeneous material, for example a plastic, which is firmly bonded to the shank. More specifically and preferably, the knitting tool is of the type wherein the shank is provided with at least one butt and includes two guide portions extending from the upper edge of the shaft to the lower edge of the shank with one of the guide portions being disposed below the butt and with both guide portions being connected together by at least one narrow web, having a maximum height of 1.1 mm, so that the web together with the guide members define a free space or opening which is filled with a vibration damping material firmly bonded to the shank.
The term "knitting tool" as used in this application is intended to include latch needles, composite needles, needles without latches, for example, plush hooks for the production of plush goods, as well as sinkers.
2. Description of the Prior Art
Federal Republic of Germany Pat. No. 3,314,908, corresponding to U.S. Pat. No. 4,562,705 which is incorporated herein by reference, discloses a stamped or punched knitting tool for flat-bed or circular knitting machines whose shank has at least one butt and at least two spaced solid guide portions which extend from the upper edge to the lower edge of the shank. One of these guide portions is aligned with and disposed below the butt. Both of the spaced guide portions are connected by at least one narrow web portion having a maximum height of 1.1 mm so that the guide portions and the web portion or portions define an opening, hole or free space in the shank. This opening is filled with a vibration damping material which is firmly bonded to the needle shank. The vibration damping material can be an elastic plastic having high damping characteristics. However, the use of other materials is not excluded.
According to the above cited patent the opening or free space defined when a single narrow web portion is used to connect two adjacent guide portions may open toward the lower or toward the upper edge of the shank. Alternatively, when two adjacent guide portions are connected together by two web portions, each having a maximum height of 1.1 mm, the opening is completely enclosed by the web portions and the guide portions. Different embodiments having one or a plurality of openings are described.
Such knitting tools, and particularly needles, have been found to be excellent in practice. It has been found that the vibration behavior of these knitting tools, when configured into a highly elastic structure having web heights of a maximum of 1.1 mm, is advantageously influenced by the vibration damping material contained in the opening, particularly when operating the tools for long periods of time and/or at very high operating speeds. Moreover, practical experience has shown that breaking of the web portions due to material fatigue or breaks of hook do not occur to a noticeable degree after long periods of operation or at high operating speeds.
However, the vibration damping material filling the opening is able to develop the above beneficial effect only if it is firmly bonded to the shank material along the edges defining the opening. Particularly for very fine knitting tools (i.e. knitting tools whose shank thickness is very small), the area defining the outline of the opening and available for a bond between the shank material and the vibration damping material is very narrow. However, particularly when such needles are utilized in particular knitting machines in which, during operation they are driven out of the needle bed to such an extent that, in the driven-out position, the opening filled with the vibration damping material projects beyond the needle bed on the side of the hooks, the needle shank may be subjected to considerable lateral forces in the region of the opening. If these lateral forces are so strong that they cause the needle shank to be noticeably deflected transversely to the longitudinal axis of the needle, the bond between the vibration damping material filling the opening and the web and guide portion edges outlining or defining the opening is subjected to very high stresses. If these stresses cause the vibration damping material to break loose from the edges defining the opening at some points, or even break out of the opening, interference with the vibration damping characteristic of the material filling the opening results. This may lead to more or less undamped transversal bending vibrations sufficient to cause material fatigue of the highly elastic needle element in the web portions of the needle with continued operation.